Nickel-chromium casting alloy with niobides



Dec. 18, 1962 F. G. HAYNEs NICKEL-CHROMIUM CASTING ALLOY WITH NIOBIDES Filed July 5l, 1959 FRA NK G. HAYNES INVENToR.

ATTORNEY United States Patent Oiilice 3,059,258 Patented Bec. 18, 1962 The present invention relates to alloys and, more particularly, to age-hardenable nickel-chromium alloys containing niobium and molybdenum.

Heretofore, the art has endeavored to produce agehardenable nickel-chromium alloys which have good casting properties when cast in the presence of air in combination with good workability and/ or excellent response l to age-hardening heat treatment. Although attempts were i 'made to provide such an alloy, none, as far as I am aware, was entirely successful when carried into practice commercially on an industrial scale.

A small amount of tantalum is commonly associated with niobium in the forms in which niobium is commercially available. For instance, niobium is available as an alloy nominally consisting of 40% nickel and 60% niobium, but one-tenth of the nominal niobium content is often tantalum. The alloys according to the invention can also contain such tantalum introduced into them with the niobium.

The alloys according to the invention contain niobides, which form a hardening phase or phases; these may be niobium compounds with nickel, cobalt, iron or chromium, such as Ni3Nb, CoZNb, FeZNb or CrgNb. Whether or not the hardening phase or phases have these compositions, they are nonetheless niobium-rich and precipitate to impart good properties, preferably by heat' treatment. It is because of the ailnity of niobium for carbon that the carbon content is controlled since only uncombined niobium is available to form the hardening phase or phases.

It has now been discovered that by employing spef cially controlled amounts of niobium and molybdenum in combination in a nickel-chromium containing alloy base, an alloy can be obtained having good casting characteristics in conjunction withrexcellent age-hardening characteristics.

'It is an object of the present invention to provide novel age-hardenable alloys.

Another object of the invention is to provide novel alloys having improved castings and age-hardening characteristics.

The invention also contemplates providing novel agehardened alloys.

It is a further object of the invention to provide a method for producing novel age-hardenable alloys.

Other objects and advantages will become apparent from the following description taken in conjunction with the accompanying drawing in which the FIGURE is a composite graph relating aging temperature of an alloy of the present invention'to stress and elongation.

Generally speaking, the present invention contemplates nickel alloys particularly for use as castings, although also useful in Wrought form, containing about 10 to about 35% chromium, about 2% to about 12% niobium, about 4% to about 16% molybdenum, together with not more than 0.2% and advantageously not more than 0.1% carbon. Silicon and manganese are both present in small amounts, say not more than 0.5% each. The alloys can also contain one or more other elements, for example, tungsten up to about 12%, cobalt up to about 40%, iron up to about 40% and more particularly up to about 5%, boron up to about 0.1%, zirconium up to about 2% and beryllium up to about 1%. At least about 25% and advantageously at least about 40% nickel must be present in the alloys together with a minimum of 8% in total of molybdenum plus tungsten in alloys of low iron content, i.e. alloys containing -5% iron. The carbon content of the alloys is related to the tungsten content so that when the alloy is devoid of tungsten the carbon content must be held below about 0.1% and advantageously below about 0.05%, e.g., about 0.03%. When tungsten is present in the alloys in amounts of at least about 3%, the carbon content of the alloys can be increased above about 0.1% to about 0.2% provided that zirconium is also co-present in amounts such that the ratio of the zirconium content to the carbon content is between about to l and 15 to l. In all cases, elements deleterious to casting, for example, titanium, are maintained at the lowest practical levels, that is, at a maximum of about 0.1%. Advantageously the alloys are devoid of titanium.

In carrying the invention into practice, advantageous results are obtained when the alloys contain about 15% to about chromium, about 4% to about 10% niobium, about 4% to'about 12% molybednum, about 3% Y to about 8% tungsten, about 0.003% to about 0.015%

boron, about 0.03% vto about 0.07% zirconium, up to about 40% iron, up to about 15% cobalt, up to about 0.4% silicon, up to about 0.3% manganese, up to about 0.03% carbon, less than 0.1% titanium, less than 0.1%

at least about 25% and advantageously at least about 40%. For the best elevated temperature characteristics, iron should be maintained within the range of up to about 5%. Iron in the range of about 25 to 40% in conjunction with both the broad and the more advanta geous compositions provides a lower level of characteristics which is useful to provide alloys having good castability. Of course, when iron is employed in these amounts, the cobalt content usually is relatively low, for example, up to about 5 Alloys both within the broad and the more advantageous ranges can be heat treated by being held in the temperature range of l050 C. to 1125o C., e.g., at 1100 C. for 8 hours, and aged at a temperature between 700 C. and 900 C., e.g., at 850 C. for 16 hours. When heat treated in this manner, the alloys of the present invention have a life to rupture of from 50 to 2,000 hours under a stress of 9 tons per square inch (isi.) Vat a temperature of 815 C. In the as-cast state, the alloys have a life to rupture of about 50 to about 1,000 hours under the same test conditions.

For the purpose of giving those skilled in the art a better understanding of the invention, a number of alloys in accordance with the teachings of the present invention are set forth in Table l.

Table I Alloy Cr, Mo, W, Nb, C, Zr, Si, Mn, Nl, No. perperperperperperperperpercent cent cent cent cent cent. cent cent; cent 8.2 7. 5 0.01 0 3 0.3 Bal. 6.1 5.9 6.0 0.03 Bal. 6.1 5.9 6.0 0.1 l 0 Bal. 6 6 6 0. 03 0. 4 0 3 Bal. 6 G 6.5 0.05 0 05 0.4 0 3 BaLl 8 3 2 0.03 0. 4 0 3 37 2 '1 Includes 4.7% cobalt and 0.01% boron.

2 Iron balance. v

The alloys were tested in various conditions as set forth in Table il.

Table I1 Treatment As Cast. A Cast in air; 8 hours at 1,080 C.; an' cooled; 16 hours at 3 Cast in air; 8 hours at 1,080 C.; air cooled; 16 hours at 800 C.; air cooled.

The alloys of the present invention exhibit good elevated temperature stress-rupture characteristics in the temperature interval of about 600 C. to about 950 C. and especially between about 750 C. and about 900 C. When stress-rupture tested at elevated temperatures, certain of the alloys set forth in Table I exhibited the characteristics as set forth in Table III.

1 Test bars used were 1% long and had a diameter of 0.252.

The alloys of the present invention also exhibit good room temperature characteristics. The results of tests conducted at room temperature are set forth in Table IV.

Table IV Proof Proof Proof Condr Prop. ,n Elonga- Alloy tion Limit, EHESS Sthss Stress U.T.S., tion No. No. t.s.i. portent l A 1 40. 0 5. 6 D 2 45. G 9 E 2 l18.8 4. 5 C 2 48. 4 6. 7 F 33. 4. 5

lTest bars used were 11,4" long and had a diameter of 0.252. It is to be noted that the aging temperature affects the room temperature tensile characteristics of the alloys of the present invention (illustrated by alloy E) as shown in the drawing. Referring now thereto, it is to be observed that when alloy No. E is aged at a temperature of about 750 C. this treatment results in optimum values of the ultimate tensile strength and the 0.1% proof stress and a minimum elongation. By varying the aging temperature of this alloy, any desired combination of room temperature characteristics within the ranges indicated can be obtained.

The alloys of the present invention are particularly adapted to be employed as components in gas turbines and other machines which are subjected to stress at elevated temperatures. Alloys containing about 25 to about 40% iron are particularly useful for the manufacture of hot-plugs for diesel engines.

Although the present invention has been described in conjunction with preferred embodiments, it is to be understood that modications and variations may be resorted to without departing from the spirit and scope of the invention, as those skilled in the art will readily understand. Such modifications and variations are considered to be within the purview and scope of the invention and appended claims.

I claim:

1. An alloy age-hardenable by precipitation of niobides which contains about 10% to about 35% chromium, about 4% to about 16% molybdenum, about 2% to about 12% niobium, up to about 0.2% carbon, up to about 5% iron, up to about 40% cobalt, up to about 0.5% silicon, up to about 0.5 manganese, up to about 2% zirconium, up to about 0.1% boron, up to about 12% tungsten, at least about 8% of tungsten plus molybdenum, up to about 1% beryllium, less than about 0.1% titanium with the balance being essentially nickel in amounts of at least about 40%, said alloy having the amounts of carbon and tungsten so interrelated that when the alloy contains less than about 3% tungsten the carbon is below about 0.1% and when the alloy contains greater than about 3% tungsten the alloy contains up to about 0.2% carbon provided that when carbon is in excess of about 0.1% the ratio of the zirconium percentage to the carbon percentage is betwen about 5 to 1 and 15 to 1.

2. An age-hardened alloy containing about to about 35% chromium, about 4% to about 16% molybdenum, about 2% to about 12% niobium, up to about 0.2% carbon, up to about 5% iron, up to about 40% cobalt, up to about 0.5% silicon, up to about 0.5% manganese, up to about 2% zirconium, up to about 0.1% boron, up to about 12% tungsten, at least about 8% of tungsten plus molybdenum, up to about 1% beryllium, less than about 0.1% titanium with the balance being essentially nickel in amounts of at least about 40%, said alloy having the amounts of carbon and tungsten so interrelated that when the alloy contains less than about 3% tungsten the carbon is below about 0.1% and when the alloy contains greater than about 3% tungsten the alloy contains up to about 0.2% carbon provided that when carbon is in excess of about 0.1% the ratio of the zirconium percentage to the carbon percentage is between about 5 to 1 and 15 to 1.

3. An age-hardenable alloy containing about 15% to about chromium, about 4% to about 12% molybdenum, about 4% to about 10% niobium, up to about 0.03 carbon, up to about 5% iron, up to about 15% cobalt, up to about 0.4% silicon, up to about 0.3% manganese, about 0.03% to about 0.07% zirconium, about 0.003% to about 0.015% boron, about 3% to about 8% tungsten, at least about 8% of tungsten plus molybdenum, less than about 0.1% each of titanium and aluminum with the balance being essentially nickel in amounts of at least about 25%.

References Cited in the le of this patent UNITED STATES PATENTS 2,246,078 Rohn et al June 17, 1941 2,397,034 Mohling Mar. 19, 1946 2,777,766 Binder Jan. 15, 1957 

1. AN ALLOY AGE-HARDENABLE BY PRECIPITATION OF MIOBIDES WHICH CONTAINS ABOUT 10% TO ABOUT 35% CHROMIUM, ABOUT 4% TO ABOUT 16% MOLYBDENUM, ABOUT 2% TO ABOUT 12% NIOBIUM, UP TO ABOUT 0.2% CARBON, UP TO ABOUT 5% IRON, UP TO ABOUT 40% COBALT, UP TO ABOUT 0.5% SILICON, UP TO ABOUT 0.5% MANGANESE, UP TO ABOUT 2% ZIRCONIUM, UP TO ABOUT 0.1% BORON, UP TO ABOUT 12% TUNGSTEN, AT LEAST ABOUT 8% OF TUNGSTEN PLUS MOLYBDENUM, UP TO ABOUT 1% BERYLLIUM, LESS THAN ABOUT 0.1% TITANIUM WITH THE BALANCE BEING ESSENTIALLY NICKEL IN AMOUNTS OF AT LEAST ABOUT 40%, SAID ALLOY HAVING THE AMOUNTS OF CARBON AND TUNGSTEN SO INTERRELATED THAT WHEN THE ALLOY CONTAINS LESS THAN ABOUT 3% TUNGSTEN THE CARBON IS BELOW ABOUT 0.1% AND WHEN THE ALLOY CONTAINS GREATER THAN ABOUT 3% TUNGSTEN THE ALLOY CONTAINS UP TO ABOUT 0.2% CARBON PROVIDED THAT WHEN CARBON IS IN EXCESS OF ABOUT 0.1% THE RATIO OF THE ZIRCONIUM PERCENTAGE TO THE CARBON PERCENTAGE IS BETWEEN ABOUT 5 TO 1 AND 15 TO
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